{"id":40599,"date":"2020-02-02T10:22:53","date_gmt":"2020-02-02T10:22:53","guid":{"rendered":"\/forum\/forums\/topic\/fluent-multiple-sliding-mesh-model-setup-queries\/"},"modified":"2020-02-02T10:22:53","modified_gmt":"2020-02-02T10:22:53","slug":"fluent-multiple-sliding-mesh-model-setup-queries","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/fluent-multiple-sliding-mesh-model-setup-queries\/","title":{"rendered":"Fluent Multiple Sliding Mesh Model Setup Queries"},"content":{"rendered":"

Hi,<\/p>\n

<\/p>\n

I’m trying to model a small 4 bladed rotor and have two hopefully small queries.  <\/span> <\/span>The model consists of a 360 mm diameter rotor with 4 blades of 70mm chord.  <\/span>The rotor rotates at 500 RPM CCW which gives a chord based Reynold’s number of approx. 40,000.  <\/span>Each of the 4 blades pitches in a sinusoidal manner to +\/-45 degrees as the rotor rotates, in one rotor rotation.  <\/span>The rotor geometry is shown in image 1 below.  <\/span><\/p>\n

<\/p>\n

To achieve the mesh motion I’ve created a Define_CG_Motion UDF for the rotor and each of the blade regions, and defined a dynamic mesh for each treating them as a rigid body.   <\/span>The moving meshes are working as they should in preview mesh motion, but one thing I am finding is that there is a velocity gradient across each of the blade interfaces as shown in image 2.  <\/span>There is a non-conformal mesh at the boundary due to each part being imported as separate bodies from Solid works.  <\/span><\/p>\n

<\/p>\n

I’ve tried conformal meshes and refined the mesh in this area to something that is really fine and the problem persists.  <\/span>Along with structured and unstructured meshes.  <\/span>I’ve also tried a 0.05mm gap at the interface and the situation is the same.  <\/span>The velocity discontinuity is typically only 1-2 mesh elements high.  <\/span><\/p>\n

<\/p>\n

I’ve checked the model setup and can’t see anything else that could cause this.  <\/span>I’ve also undertaken a time step sensitivity analysis down to 0.25deg\/step and it’s still the same.  <\/span>I am solving the problem with the k-ω SST model with low Reynold’s Correction.  <\/span>I’m using a coupled based solver and have the residuals set to 1e-4.<\/p>\n

<\/p>\n

The overall geometry extends to 20 x rotor diameter on all sides.   <\/span>The rotor is essentially a small rotor in a large room with no imposed free stream velocity.  <\/span>The rotor generates its own wake so I have assigned each of the boundary conditions as symmetry so the normal velocity component and pressure at the symmetry plane is zero.  <\/span>I am not sure if this is the best boundary condition?  <\/span>If I used a velocity inlet it would be zero.<\/p>\n

<\/p>\n

Any information on the two queries would be much appreciated.<\/p>\n

<\/p>\n

\"\"<\/p>\n

<\/p>\n

\"\"<\/p>\n","protected":false},"template":"","class_list":["post-40599","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_old_topic_id":["12779"],"_bbp_old_topic_author_name_id":["Anonymous"],"_bbp_old_is_topic_anonymous_id":["false"],"_bbp_old_closed_status_id":["publish"],"_bbp_author_ip":[null],"_bbp_old_sticky_status_id":["normal"],"_bbp_likes_count":["0"],"_btv_view_count":["2402"],"_bbp_subscription":["247047"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["40599"],"_bbp_forum_id":["27792"],"_bbp_engagement":["199","172769"],"_bbp_voice_count":["2"],"_bbp_reply_count":["9"],"_bbp_last_reply_id":["106038"],"_bbp_last_active_id":["106038"],"_bbp_last_active_time":["2020-02-20 17:17:51"]},"test":"engineer86"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/40599","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/40599\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=40599"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}